The present embodiments generally pertain to heat exchangers utilized with gas turbine engines. More particularly, the present embodiments relate to surface conforming heat exchangers which utilize a dual seated by-pass valve.
In a gas turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. A typical gas turbine engine generally possesses a forward end and an aft end with its several core or propulsion components positioned axially therebetween. An air inlet or intake is located at a forward end of the gas turbine engine. Moving toward the aft end, in order, the intake is followed by a compressor, a combustion chamber, and a turbine. It will be readily apparent from those skilled in the art that additional components may also be included in the engine, such as, for example, low-pressure and high-pressure compressors, and low-pressure and high-pressure turbines. This, however, is not an exhaustive list. In a typical turbo-prop gas turbine engine aircraft, turbine stages extract energy from the combustion gases to turn a turbo-propeller. In some embodiments, the propulsor may power one or more turbo-propellors (hereinafter, “turbo-prop”) in the case of some airplanes. In alternate embodiments, the propulsor may drive one or more turbo-propellers, embodied as rotors, for operation of a helicopter.
During operation, significant heat is generated by the combustion and energy extraction processes with gas turbine engines. It is necessary to manage heat generation within the engine so as not to raise engine temperatures to unacceptable levels, which may cause engine failure. One method of controlling heat and improving engine life is to lubricate engine components and cool lubricating fluids. In such heat exchanger embodiments, the air stream is utilized to cool the hot fluid of the turbine engine.
Certain valve arrangements may be utilized wherein when engine cooling fluid is hot, the valve arrangement causes the cooling fluid to flow only through the core of the heat exchanger. In some embodiments, when the engine cooling fluid is cool, the valves allow simultaneous flow through core portion of the heat exchanger and de-congeal channels.
However, when the engine is non-operational or is operating in circumstances where the engine is subjected to subzero temperatures, cooling of the lubricating fluid is not required. In fact, it may be the case that cooling of the fluid in these conditions may cause freezing of water in engine fuel within the engine creating blockages with potentially catastrophic results. In these sub-zero conditions, the lubricating fluid may be, or may become, congealed, that is the fluid may have high viscosity and more resistant to flow, having increased operating pressure.
It would be desirable to overcome these situations and allow for controlled heating of the heat exchanger to de-congeal without necessarily passing fluid also through the core cooling channels of the heat exchanger.
The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded subject matter by which the scope of the innovation is to be bound.